Preheat your oven to 350 F and place mini cupcake liners in two 12-count mini cupcake tins (or put standard-sized cupcake liners in one 12-count standard-sized cupcake tin). Set aside.,In a large bowl, whisk together the flour, baking powder, baking soda and sea salt. Set aside.,In another large bowl, whisk together the butter, shortening and sugar until combined. Add the whole milk, sour cream, egg and vanilla extract. Whisk until smooth and creamy.,______,Divide the batter among the 24 mini-liners (or 12 standard-size liners), filling them 3/4 of the way full.,Bake at 350 F for 10-11 minutes for mini-cupcakes (20-22 minutes if using standard-size muffin tin) or until a toothpick inserted into the center of one comes out clean (or with just a few crumbs). Remove from oven and let cupcakes cool completely.,While the cupcakes are cooling, prepare your frosting. In the bowl of a stand mixer, with paddle attachment fixed, cream together the butter and cream cheese until light and fluffy. Add the confectioner's sugar while the mixer is set to low speed. Once all of the sugar has been added, add the heavy cream, vanilla extract and salt. Increase the speed to medium, and mix for 2 minutes. If the frosting is too thick, add more heavy cream (a tablespoon at a time). If it is too thin, add more sugar (a tablespoon at a time), until you get the consistency you desire.,Frost each cupcake using your desired method and sprinkle with sprinkles. Store in an airtight container, at room temperature, for up to a week. Enjoy!